148 



POULTRY DISEASES 



or oven nnicli larger. It iiiay 1)0 accompanied by 

 roup; in fact, wo have studied botli diseases in tli<' 

 same flock, an occnrrence wliicli is not uncommon. 

 The question naturally arises, are both due to fil- 

 terable viruses (g'orms so small that they pass 

 through porcelain filters, and too small to be seen 

 through a microscope), and are both present in 



Fig. 46. Chicken Pox 

 A, Epithelial, tiimor-likc nodules. B, an ulcer. 



the same outbreak, or are both due to the same 

 cause? At the present time there are conflicting 

 reports by scientific men. Fig. 46 illustrates a 

 case of this disease. 



One investigator has reported that immuniiy 

 against chickenpox does not confer immunity to 

 roup. 



Haring and Kofoid have shown that there is a specific 

 antibody developed in birds affected with chickenpox. By 



